A pilot and two passengers have died when a light aircraft crashed just north of Mount Gambier in South Australia's south-east.

The victims were 78-year-old Adelaide Hills man, Grant Gilbert,who was piloting the aircraft, and a 43-year-old woman and a 16-year-old girl, both from Mount Gambier.

Mr Gilbert became the licence holder and operator of the 25-year-old single-engined plane in early 2014, and flew it mainly between Adelaide, Mount Gambier, Port Lincoln and Murray Bridge, according to aviation records.

State MP Michael Pengilly said he was saddened his good friend Mr Gilbert was killed, and for the tragic loss of the two female victims.

"Grant and I go back 20 years, when he was my deputy chair of the regional health board and our friendship continued over the years," he said.

"He was a tireless community man and a very good businessman. A true and loyal husband and father."

Plane extensively damaged on impact

The plane crashed into a paddock in Suttontown, just south-west of Mount Gambier's airport, just before 10:30am.

There were no survivors from the crash and the local fire service said the plane was extensively damaged.